Updating Opus to a pre-release of 1.1

This CL updates Opus to a pre-release of the coming Opus 1.1 version. The code is extracted from http://git.xiph.org/?p=opus.git, commit aee4d8057632ea0cfc1d55d88acf8466b47b7b4b from October 1st 2013.
This version includes both algorithmic and platform optimizations, as well an important fix for a denorm problem when the input goes silent after active audio. The problem causes high CPU usage.

Review URL: https://codereview.chromium.org/28553003

git-svn-id: svn://svn.chromium.org/chrome/trunk/deps/third_party/opus@230378 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/include/opus_multistream.h b/include/opus_multistream.h
index 658067f..ae59979 100644
--- a/include/opus_multistream.h
+++ b/include/opus_multistream.h
@@ -205,6 +205,12 @@
       int coupled_streams
 );
 
+OPUS_EXPORT OPUS_WARN_UNUSED_RESULT opus_int32 opus_multistream_surround_encoder_get_size(
+      int channels,
+      int mapping_family
+);
+
+
 /** Allocates and initializes a multistream encoder state.
   * Call opus_multistream_encoder_destroy() to release
   * this object when finished.
@@ -258,6 +264,17 @@
       int *error
 ) OPUS_ARG_NONNULL(5);
 
+OPUS_EXPORT OPUS_WARN_UNUSED_RESULT OpusMSEncoder *opus_multistream_surround_encoder_create(
+      opus_int32 Fs,
+      int channels,
+      int mapping_family,
+      int *streams,
+      int *coupled_streams,
+      unsigned char *mapping,
+      int application,
+      int *error
+) OPUS_ARG_NONNULL(5);
+
 /** Initialize a previously allocated multistream encoder state.
   * The memory pointed to by \a st must be at least the size returned by
   * opus_multistream_encoder_get_size().
@@ -316,6 +333,17 @@
       int application
 ) OPUS_ARG_NONNULL(1) OPUS_ARG_NONNULL(6);
 
+OPUS_EXPORT int opus_multistream_surround_encoder_init(
+      OpusMSEncoder *st,
+      opus_int32 Fs,
+      int channels,
+      int mapping_family,
+      int *streams,
+      int *coupled_streams,
+      unsigned char *mapping,
+      int application
+) OPUS_ARG_NONNULL(1) OPUS_ARG_NONNULL(6);
+
 /** Encodes a multistream Opus frame.
   * @param st <tt>OpusMSEncoder*</tt>: Multistream encoder state.
   * @param[in] pcm <tt>const opus_int16*</tt>: The input signal as interleaved